The interventional procedure known as "percutaneous transluminal angioplasty" (PTA) is commonly employed to treat arterial stenosis. In the conventional PTA procedure, a preshaped guide wire is introduced into an artery and advanced until the distal end of the guidewire is beyond the point of arterial buildup. A balloon-tipped catheter is then pushed over the guide wife until the balloon resides within the narrowed portion of the artery. The balloon is inflated in order to compress arterial buildup against the inner wall of the artery so as to allow the unrestricted flow of blood.
PTA, or "balloon surgery" as it is sometimes known, is the primary treatment for intravascular stenosis. In the context of coronary arteries, the procedure is referred to as percutaneous transluminal coronary angioplasty, or PTCA. Approximately 600,000 balloon angioplasty procedures are performed in the United States annually, consuming $5,000,000,000.00 of health care resources. Percutaneous transluminal coronary angioplasties represent 400,000 of these procedures.
PTA and PTCA have enjoyed a high success rate for correcting arterial blockage. These procedures are much less invasive than bypass surgery. Unfortunately, arteries which have undergone balloon angioplasty have demonstrated a propensity towards restenosis. As discussed in U.S. Pat. No. 5,616,114 to Thornton, et al, restenosis occurs "as a result of injury to the arterial wall during the lumen opening angioplasty procedure." Injury to the arterial wall stimulates hyperplastic growth of the vascular smooth muscle cells. It is this smooth muscle growth that renarrows the vessel lumen, necessitating a repeat angioplasty or, perhaps, surgical revascularization.
A procedure in development for reducing the restenosis rate is the introduction of radiation energy into the interior of the vessel. This procedure, known alternately as Intravascular Radiation Therapy (IRT) or brachytherapy, has been shown to inhibit fibroblast and smooth muscle cell hyperplasia. Various methods for introducing radiation into an area treated for stenosis are known. Some methods deliver radiation in a solid medium, while others utilize liquid sources.
U.S. Pat. No. 5,059,166 to Fischell discloses an IRT method that relies on a radioactive stent that is permanently implanted in the blood vessel after completion of the lumen opening procedure. U.S. Pat. No. 5,302,168, issued to Hess, teaches use of a radioactive source contained in a flexible catheter with remotely manipulated windows. U.S. Pat. No. 5,503,613 to Weinberger uses a liquid filled balloon to guide a solid source wire to a treatment site. U.S. Pat. No. 5,616,114, to Thornton, et al, describes an apparatus and method, for delivering liquid radiation into a balloon-tipped catheter. In Thornton's method, expansion of the balloon by injection of the radioactive liquid serves the dual function of expanding the blockage and relieving the stenosis, while at the same time irradiating the tissue. Finally, it is known in the art to transiently place seeds of a radioactive substance into the vessel by means of a wire.
The use of radioactive materials in connection with an angioplasty procedure creates a risk of harmful exposure, both to the medical personnel and to the patient. Precautionary measures have been incorporated to protect against the leakage of liquid radiation into the blood stream during angioplasty. See, for example, U.S. Pat. No. 5,616,114, to Thornton, et al. wherein a closed catheter system is employed. However, the prior art fails to disclose an apparatus by which medical staff and patients can be shielded from radiation prior to the introduction of the radioactive substance into the catheter.
In the context of liquid IRT, the known procedure for introducing radiation into an angioplasty catheter is by loading liquid radiation into a bore syringe. The syringe, in turn, is placed in fluid communication with the balloon-tipped catheter. Various radiation sources have been used for IRT. Examples of these include Strontium 90 (.sup.90 Sr), Iridium 192 (.sup.192 Ir), Phosphorous 32 (.sup.32 P), Rhenium 186 (.sup.186 Re) and Rhenium 188 (.sup.188 Re). However, it is appreciated that all of these sources emit radiation which presents a risk of harm from exposure.
The apparatus and method employed by medical staff today to provide shielding from radiation is use of a lead apron. The operator of the angioplasty assembly and the assisting medical staff are draped in aprons which are impermeable to radiation. However, it is evident to those skilled in the medical art that the lead apron does not insulate radiation within the angioplasty catheter assembly; rather, it only shields those parts of the body covered by the lead apron. Uncovered parts such as the hands and face remain exposed. Exposure to radiation is exacerbated by the process employed to load radiation into an angioplasty catheter assembly. First, the operator is required to manually load the radioactive liquid into the inflation syringe. This creates a hazard of exposure to radiation emanating from the syringes, and also creates a risk that the operating field may become contaminated in the event of a leak during the loading process. Second, there is a risk of leakage during the process of irradiating tissue, Those skilled in the art will appreciate that the connectors used to connect the inflation syringe with the other parts of the angioplasty catheter assembly are detachable and may become disconnected.
An apparatus and method are needed which will protect the medical staff and patient from radiation exposure during the angioplasty procedure. The prior art fails to disclose an apparatus by which medical staff and patients can be shielded from radiation emanating from the angioplasty catheter assembly during IRT. Medical packages such as the one disclosed in U.S. Pat. No. 5,165,540, to Forney, Y-adaptors such as the one disclosed in U.S. Pat. No. 5,395,352 to Penny, and inflation syringes such as the one disclosed in U.S. Pat. No. 5,429,606, all of which have utility to the operation of an angioplasty catheter, do not work together to speak to or teach an apparatus which will shield the medical staff and patient from radiation. Additionally, prior art fails to teach an apparatus and method by which radioactive liquid can be loaded into an angioplasty syringe at the radiopharmacy, and then transported to the operating room in a sterile and radiation shielded manner.
It is an object of the present invention to provide a catheter assembly having nondetachable connections so as to reduce the risk of leakage of liquid radiation during the radiation injection process.
It is also an object of the present invention to provide a sterile package for a catheter assembly which provides a unique injection port through which liquid radiation may be loaded by the radio-pharmacist at the pharmacy into an inflation syringe. In this manner, the catheter operator is not required to transfer liquid radiation during angioplasty. This removes the risk of exposure to the medical staff and patient during the delicate loading process. It further avoids the risk that radioactive liquid might fall onto the angioplasty table or elsewhere, thereby contaminating the operating field.
It is further an object of the present invention to provide an inflation syringe for injecting liquid radiation into a catheter, wherein the syringe is fabricated to limit radiation exposure.
Finally, it is an object of the present invention to provide a method for performing intraluminal radiation therapy which includes the use of radiation insulated carrying cases which allow the transportation of the loaded angioplasty catheter assembly from the radiopharmacy to the operating room in a sterile and radiation shielded environment, and from the operating room to an appropriate disposal site.